This invention relates to image sensors, also referred to herein either as photo imagers, photo sensors or simply as "imagers". In particular, this invention relates to an imager capable of capturing a predetermined number of frames at a very high frame rate. A "frame" of information as used herein refers to the image sensed by a photosensor array during one sampling interval. That is, a "frame" includes all the information sensed by, and read out from, all the photo sensing elements of a photosensor array during one sampling interval. Thus, a frame corresponds, in essence, to a "snapshot".
There is a need for image sensors capable of, for example, capturing images of rapid motion and transient photometric phenomena. In general, there is a need for photo imagers capable of sensing and capturing photo signals changing at a very high rate and for storing the information captured such that it can be subsequently read out at a different (e.g., slower) rate. More specifically, there is a need for a photo imager capable of sensing and storing a high number of frames while operating at a very high frame rate during a data (e.g. image) acquisition phase. For example, such an image sensor system should be capable of capturing several hundred, or more, frames at a frame rate of a million (or more) frames per second.
Circuits and systems embodying the invention enable the construction of an image sensor system capable of capturing a high number of frames at a very high frame rate.